Effect of Chemical Composition on Texture Using Response Surface Methodology

This study explores the effect of annealing temperature and chemical composition on crystallographic texture evolution of commercially pure aluminium alloy sheets using response surface methodology (RSM). The orientation of the crystal structure in Euler space using Bunge notation has been studied to know the behavior of the metal and estimate its volume fraction. The experimental procedure involves texture analysis with respect to annealing temperature and chemical composition in correlation with the results of formability and use of RSM. The effect of important input parameters, namely, annealing temperature and chemical composition (impurities) was used for predicting the numerical models using the volume fraction of texture output from the crystallographic study using Design Expert 8.0.7.1, trial software. Also this study explains the effect of individual chemical components, namely, iron, silicon, and copper in evolution of texture components. The volume fraction of Cube {1 0 0} 〈0 0 1〉, Bs {1 1 0} 〈1 1 2〉, and S {1 2 3} 〈6 3 4〉 components increase, whenever iron and copper content increase and silicon component decreases.     

基于响应曲面法的Ar-N2 等离子射流特性研究

目的研究等离子射流特性,提高射流品质,为工程实践提供支撑。方法通过响应曲面法,以粒子速度和温度为指标反映射流特性的变化,采用Box-Behnken-Design(BBD)设计分析电流(I)、主气流量(Q)以及次级气比例(C)对于射流特性的影响规律及其相互作用关系。结果对粒子速度的影响因素排序为Q_(Ar)IC,对粒子温度的影响因素排序为IQ_(Ar)C。该喷嘴下实现最佳加热效应的参数为:主气流量80 L/min、电流450 A、次级气比例22.5%。实现射流最佳加速效应的离子气及电参数为:主气流量140 L/min、次级气比例15%、电流400 A。在射流最佳加速效应对应参数下制备的AT40涂层均匀致密、孔隙少。结论运用响应曲面法分析和解决等离子射流特性影响问题具有科学性和可操作性,能够有效指导涂层制备。     

Fabrication and Wear Behavior of Nanostructured Plasma-Sprayed 6061Al-SiCp Composite Coating

6061Al powder with 15 wt.% SiC particulate (SiC_p) reinforcement was mechanically alloyed (MA) in a high-energy attrition mill. The MA powder was then plasma sprayed onto weathering steel (Cor-Ten A242) substrate using an atmospheric plasma spray process. Results of particle size analysis and scanning electron microscopy show that the addition of SiC particles as the reinforcement influences on the matrix grain size and morphology. XRD studies revealed embedment of SiC_p in the MA-processed composite powder, and nanocrystals in the MA powder and the coating. Microstructural studies showed a uniform distribution of reinforced SiC particles in the coating. The porosity level in the coating was as low as 2% while the coating hardness was increased to 232VHN. The adhesion strength of the coatings was high and this was attributed to higher degree of diffusion at the interface. The wear rate in the coatings was evaluated using a pin-on-disk type tribometer and found to decrease by 50% compared to the 6061Al matrix coating. The wear mechanism in the coating was delamination and oxidative type.     

Quantitative Modeling for Corrosion Behavior in Complex Coupled Environment by Response Surface Methodology

Response surface methodology(RSM) is introduced into corrosion research as a tool to assess the effects of environmental factors and their interactions on corrosion behavior and establish a model for corrosion prediction in complex coupled environment(CCE). In this study, a typical CCE, that is, the corrosion environment of pipelines in gas field is taken as an example. The effects of environmental factors such as chloride concentration, pH value and pressure as well as their interactions on critical pitting temperature(CPT) were evaluated, and a quadratic polynomial model was developed for corrosion prediction by RSM. The results showed that the model was excellent in corrosion prediction with R2= 0.9949. CPT was mostly affected by single environmental factor rather than interaction, and among the whole factors, chloride concentration was the most influential factor of CPT.     

A Study of Pack Aluminizing Process for NiCrAlY Coatings Using Response Surface Methodology

Aluminizing process is widely used to provide additional Al deposition onto superalloy surface for enhanced oxidation and corrosion resistance. In this research, an aluminizing process—pack cementation process, is used to deposit Al onto the surface of NiCrAlY coatings for increasing environmental protection. The experiment is designed using Box-Behnken approach, in which three parameters, the Al content, Ni content of the pack powder, and the temperature of the process, are selected as factors; and the thickness and Al/Ni ratio of the coatings are selected as responses. The effects of the factors on the responses are analyzed and modeled empirically. It is found that these empirical models correlate well with the results from additional sets of experiment. These models can be used to produce aluminized NiCrAlY coatings with specific thicknesses and Al/Ni ratios.     

Corrosion and Wear Response of Oxide-Reinforced Nickel Composite Coatings

Various grades of fuels are used in automobiles, as a result the engine components are continuously subjected to simultaneous action of corrosion and wear. Ni-SiC composite coating is the most widely investigated and commercialized wear-resistant coating in the automotive industry. However, this coating cannot be used at temperatures above 450 °C due to the tendency of SiC to react with Ni and form brittle silicides. An alternate approach is to use oxide-reinforced coatings. In the present study, zirconia, ZrO₂ and, yttria-stabilized zirconia, YSZ-reinforced Ni composite coatings have been developed by electrodeposition method. It was observed from the microhardness studies that there is no significant difference in the values for Ni-SiC and Ni-ZrO₂ coatings. The corrosion behavior was evaluated using polarization and electrochemical impedance studies. The studies showed that oxide particle-reinforced Ni coatings possessed better corrosion resistance due to their lower corrosion current density, I _corr. Tribo-corrosion studies were carried out to understand the synergistic effect of wear and corrosion on the performance of Ni-based composite coatings in 0.5 M Na₂SO₄. Among various composite coatings, Ni-YSZ exhibited less material loss thereby showing better tribo-corrosion behavior.     

Wear and Life Characteristics of Microwave-Sintered Copper-Graphite Composite

Copper-graphite composite is an important tribological material used in electrical sliding contact applications like electrical brushes in motors and generators. The electrical sliding contact experiences multiple stresses such as mechanical pressure and temperature. Traditional life tests under normal operating condition would be a time-consuming process due to the longer expected life of the composite. Accelerated wear testing was carried out to evaluate the life characteristics of the composite. This work focuses on evaluation of tribological performance of microwave-sintered copper-graphite composite using accelerated wear testing methodology using high temperature pin-on-disc tribometer. Microstructural studies of worn out surfaces were carried out using SEM with EDAX. Reliability and analysis on life characteristics were performed on the time-to-failure data using temperature-nonthermal-accelerated life-stress model. The obtained times-to-failure data from the accelerated wear testing was extrapolated to normal usage condition. Temperature and pressure are significantly affecting the wear performance. Self-lubricating action of graphite and improvement in wear resistance is helpful in extending the life of copper graphite composite. The life of the composite obtained through testing at mean and 99% reliability are 18,725 and 16,950 h, respectively.     

Prediction of Compressive Strength of Biodegradable Mg–Zn/HA Composite via Response Surface Methodology and Its Biodegradation

This work aimed to fabricate magnesium zinc/hydroxyapatite(Mg–Zn/HA) composite via powder metallurgy method and to develop a mathematical model to predict the compressive strength of the composite using response surface methodology method. The effect of various mechanical milling parameters, milling speed(200–300 r/min), ball-to-powder weight ratio(5–12.5)and HA content(2.6–10 wt%) on the compressive strength of Mg–Zn/HA composite was investigated. The model shows that high compressive strength of Mg–Zn/HA composite was achieved when the powders were prepared with high milling speed and ball-topowder weight ratio and low HA content. The mathematical model was adequate with error percentage lower than 3.4%. The microstructure of Mg–Zn/HA composite with different process parameters revealed that fine microstructure was observed at high milling speed and ball-to-powder weight ratio while agglomeration of HA was found in composite with 10 wt% HA. The agglomeration of HA led to degradation of interfacial bonding strength between matrix and reinforcement phases and hence decreased the overall compressive strength of Mg–Zn/HA composite. Biodegradation test revealed that sample with higher HA content had more weight gain and there was more formation of hydroxyapatite. Mg–Zn/HA composite with 8 wt% HA was found to be the best candidate for implant application because it had considerable compressive strength and good biodegradation properties.     

6061铝合金激光熔覆铜基复合涂层组织及磨损性能

利用激光熔覆工艺在6061合金表面熔覆铜基复合涂层,分析熔覆涂层的微观组织及化学成分,考察熔覆合金成分变化对涂层质量、硬度以及磨损性能的影响.结果表明,熔覆层主要由(Cu,Ni)固溶体、Cu9Al4、AlFe0.23Ni0.77以及CoFe增强相等组成.优化成分条件下,Fe含量为7%,Co含量为9%,熔覆层硬质颗粒体积分数增大,大量硬质颗粒增强体弥散分布在熔覆层Cu-Ni固溶体合金基体组织中,大大增强了基体的抗磨损性能.激光熔覆后的熔覆层表面硬度比6061铝合金提高了4.5倍;磨损体积约为铝合金基线的30%,摩擦因数降至0.3002.     

磨料条件下DLC复合微织构表面的磨损机理*

钛及其合金具有优良的性能被广泛应用于武器装备领域,但在磨料条件下易黏着、不耐磨的特性限制了其使用。为了提高钛在磨料作用下的减摩抗磨性能,以 TA2 钛为研究对象,使用激光加工技术在 TA2 样品表面上制备点阵微织构,然后采用磁控溅射技术在点阵微织构表面制备类金刚石碳（Diamond-like Carbon, DLC）薄膜,形成 DLC 复合微织构;采用 MS-T3000 摩擦磨损试验机研究了 DLC 复合微织构表面在磨料作用下的摩擦磨损性能,并通过扫描电子显微镜、能谱分析、 拉曼测试、有限元分析等手段研究钛表面 DLC 复合微织构的摩擦磨损机理。结果显示 DLC 复合微织构表面可有效提高钛在磨料条件下的减摩抗磨性能,且同等条件下,点阵密度对 DLC 复合微织构样品表面摩擦因数的影响最大,单位面积点阵边缘密度值与样品表面磨损率有关,且二者基本呈正线性关系。揭示了 DLC 复合微织构在磨粒磨损条件下的摩擦磨损性能, 并从织构边缘的破坏提出磨损机理,研究结果可为钛在磨料磨损条件下的应用提供理论和设计依据。     

灰铸铁件表面粒子增强复合材料的磨粒磨损特性

利用优化的涂覆铸造工艺,在灰铸铁表面复合ＷＣ增强相／高铬铸铁耐磨材料的基础上,艰复合材料的磨拉磨损特性进行了试验研究。结果表明,与淬火态６５Ｍｎ钢和４５钢相比,复合材料的耐磨性提高幅度较大,但复合材料中的增强相含量有一最佳值,因只有增强相与高强度基体结合牢固,才能充分发挥出增强相抵抗磨粒犁削的潜力。     

钒铬表面复合层的干滑动摩擦磨损性能

采用消失模铸渗的方法在铸钢件表面制备了钒铬复合层,用MM200型摩擦磨损试验机研究了不同渗剂成分试样的干滑动摩擦磨损性能,并用扫描电镜观察了试样的磨损形貌,分析了复合材料的磨损机理.结果表明:与基体材料相比,复合层的耐磨性显著提高,其最大磨损率仅是基体材料的1/8;随着载荷的增大和渗剂中钒铁含量的减少,表面复合层的磨损率提高;表面复合层的磨损机理主要是氧化磨损和裂纹的形成、扩展所造成疲劳剥落.     

响应面法优化空气喷嘴雾化流场的数值研究

为提高空气喷嘴的喷涂性能,采用计算流体力学对空气喷嘴与喷涂面之间的雾化流场进行数值模拟,并结合响应面法对喷嘴的结构参数与工况参数进行总体优化.首先搭建热线风速仪测速实验台验证数值计算模型的准确性,然后设计三因素的中心复合试验,建立以塑形气孔斜面倾角α、环形气孔压力p1、塑形气孔压力p2为设计变量,以喷涂面中心压力pc为...     

弧齿锥齿轮齿面数学建模方法

弧齿锥齿轮的精确3D几何模型是虚拟装配、接触性能分析和精密测试的基础.由于弧齿锥齿轮齿面属于复杂曲面,形状和结构较复杂,当今的齿面成型技术还不成熟,以至于齿面无法精确成型.为提高齿面成形精度,研究一种快速精确的齿面成形方法.以齿轮啮合原理为理论依据,MATLAB为主要运算工具,精确输出齿面点三维坐标;采用3D建模软件S...     

基于响应曲面法的表面粗糙度预测模型研究

分析以往建立表面粗糙度预测模型方法的不足,采用响应曲面法（RSM）建立了钢及其合金铣削加工表面粗糙度预测模型。经检验,该模型预测精度高,泛化能力强,且可简便预测铣削参数对已加工表面的表面粗糙度的影响,有助于准确认识已加工表面质量随铣削参数的变化规律,为切削参数的优选和表面质量的控制提供了依据。     

Multiobjective Optimization of Atmospheric Plasma Spray Process Parameters to Deposit Yttria-Stabilized Zirconia Coatings Using Response Surface Methodology

Atmospheric plasma spraying is used extensively to make Thermal Barrier Coatings of 7-8% yttria-stabilized zirconia powders. The main problem faced in the manufacture of yttria-stabilized zirconia coatings by the atmospheric plasma spraying process is the selection of the optimum combination of input variables for achieving the required qualities of coating. This problem can be solved by the development of empirical relationships between the process parameters (input power, primary gas flow rate, stand-off distance, powder feed rate, and carrier gas flow rate) and the coating quality characteristics (deposition efficiency, tensile bond strength, lap shear bond strength, porosity, and hardness) through effective and strategic planning and the execution of experiments by response surface methodology. This article highlights the use of response surface methodology by designing a five-factor five-level central composite rotatable design matrix with full replication for planning, conduction, execution, and development of empirical relationships. Further, response surface methodology was used for the selection of optimum process parameters to achieve desired quality of yttria-stabilized zirconia coating deposits.     

不锈钢表面等离子复合处理提高耐磨性的研究

对粉碎食品用胶体磨中的由9Crl8、3Crl3不锈钢制造的转子和定子,首先进行等离子W-Mo共渗,然后进行表面等离子超饱和渗碳,并直接进行高压气体淬火、真空低温回火处理的等离子复合处理技术,提高了转子和定子的表面硬度和耐磨性,延长了使用寿命。结果表明,不锈钢表面合金层W、Mo含量（质量分数,下同）分别达到20％和10％以上。经等离子超饱和渗碳后,表面碳浓度达到2．4％～2．6％。高压气体淬火和低温回火后的表面硬度达到64HRC～66HRC。合金层组织为马氏体基体上分布着细小、均匀的碳化物。淬火后的基体硬度为53HRC～55HRC。基体高的强韧性和适当的硬度配合,表面高的硬度和耐磨的组织,使转子和定子寿命由过去只进行真空淬火和空气炉中回火工艺处理的6～10天,提高到50天以上。     

TA1钛合金的表面复合强化与磨损行为研究

目的 针对钛合金硬度低、耐磨性差的问题,利用机械球磨技术在TA1钛合金表面获得复合强化层,研究强化层的组织结构对合金磨损行为的影响。方法 采用行星式机械球磨装置,以WC粉末为增强介质,在0.05 MPa氮气气氛、转速为350 r/min、时间为8 h的条件下,对TA1钛合金进行表面机械变形+固相涂层复合强化处理,利用光学3D轮廓仪、XRD、SEM-EDS、往复式磨损机等对复合强化层的组织结构和耐磨性能进行测试。结果 当表层机械复合强化后,TA1钛合金表面的复合强化层由WC涂层+形变细晶区组成,硬化区厚度为20~40μm,形变细晶区厚度约为30μm。涂层区硬度达到1 100HV0.25,为基材硬度的5倍。在5 N载荷下,摩擦因数为0.2~0.3,并可保持近4 000 s,在10 N载荷下,摩擦因数接近0.2并可保持1 200 s。可将磨损过程分为低摩擦因数区、过渡区和高摩擦因数区3个阶段,且每阶段的磨痕深度、磨损量与摩擦因数具有正相关性。结论 表层机械复合强化可大幅提升TA1钛合金表层的硬度和耐磨性,WC颗粒增强涂层具有较强的减摩效果,其磨损机制主要是磨粒磨损与氧化磨损。这种一步法表面强化技术具有工艺简单、能耗少、涂层选材灵活的优势。     

TiC-Fe表面梯度复合材料的磨损性能及计算机辅助分析

采用原位合成技术制备出了Ti C-Fe表面梯度复合材料,通过微区组织观察、显微硬度测试和磨损实验,并借助于计算机对实验数据进行统计分析,对复合材料的硬度以及耐磨性能进行了研究。结果表明,Ti C陶瓷层的最高显微硬度约为标准灰铸铁的20倍,耐磨性能约为标准灰铸铁的26.89倍。     

基于响应面法的铁表面PTFE涂层的使用寿命研究

目的模拟生活中不粘锅的使用环境,采用响应面法预测铁表面PTFE涂层的使用寿命,为生活中合理使用不粘锅提供支撑。方法通过响应面法考察转速和载荷对铁表面PTFE涂层使用寿命的影响,采用中心组合试验设计(CCD)考察载荷以及转速对于铁表面PTFE涂层使用寿命的影响及其相互作用。结果载荷和转速对于涂层使用寿命的影响都极为显著,检验值(F)都小于0.0001。通过试验设计软件得出使用寿命与转速和载荷的二阶多项式方程,并且复相关系数R2为0.9951,能解释99.51%响应值的变化,因此模型能够较准确地预测铁表面PTFE涂层的使用寿命。该实验工况下铁表面PTFE涂层的最佳使用参数分别为转速200r/min和载荷25 N,此时涂层寿命为147 min左右。结论模拟日常生活中使用不粘锅的实际情况,并运用响应面法分析和预测PTFE涂层的使用寿命具有科学性和可操作性,能够很好地指导生活中安全使用不粘锅。